How do I ask the guy i like who also likes me out when we're both shy?

So I'm a 16 year old girl almost in her Junior year of high school and the guy I like is a 19 year old guy who like me first but I didn't like him than over so months I started to like him a lot and then he went to the army reserved, but before that we were getting to know each other. On Thanksgiving I sent him a text that says "I like you" and he responded "I like you too" so after that nothing really happened he's also my older sister's and her boyfriend's friend that's how I first meant him but anyway we started to text each other a lot, and he was always there to make me feel better when I'm crying or upset; so I wrote him a letter because right now he's in Oklahoma in basic training but he leaves basic this Friday and I received his letter back on June 10th and he said that he was happy that I'm still his wife (Not that we're married he just calls me that) And that he still likes me a lot...he's a gentleman and a kind, caring person. He'll be back in August so I'm wondering if I should ask him out or wait a little while or not do it at all...I'm just scared of rejection that its stopping me from asking him out so I'm so confused on what to do...